It is well known to thiose skilled in the art that elongated sheets of metal derived from rolls of metallic stocks, such as steel or the like, are subsequently sheared longitudinally to provide the raw material for various fabricating operations.
During the shearing process, it is inevitable that the resulting edge is somewhat deformed and irregular because of the fact that the shearing process is, essentially, constituted by a refined and controlled tearing of the metal.
This is more frequently the case where shearing tools, such as knives, saws and the like, become slightly dulled and a gradually more imperfect edge is imparted to the sheared sheet.
Because of difficulties in controlling the shearing process, it is customary in the metal-forming arts to provide a foldover edge on most articles fabricated from raw sheared metal to eliminate the inherent mechanical and esthetic difficulties arising from the utilization of sheared sheet metal.
Obviously, in addition to injecting an additional and expensive step into the fabricating process, the foldover edge consumes an additional quantity of metal which, in large production runs, can result in substantial expense to the fabricator.
It is well known to those skilled in the art that metals can be cut or removed by the use of various types of thermo-chemical and thermoelectrical cutting or severing.
Exemplary of such methods and apparatus are those shown in U.S. Pat. Nos. 1,957,351; 2,125,180; 3,266,552; 2,184,560; 2,288,026; and 2,470,999.
The aforementioned patents disclose methods of removing or cutting metals. For instance, U.S. Pat. No. 1,957,351 discloses a method of removing metal by the use of a welding nozzle and a highly oxidizing gas stream.
The only patent of the aforementioned group of patents which is concerned with forming an edge on metal members is U.S. Pat. No. 2,184,560 which discloses a method and apparatus for thermo-chemically cutting or severing ferrous metal bodies and for forming shaped edges on metal members.
The method of the U.S. Pat. No. 2,184,560 patent involves the application of a low velocity gaseous metal removing medium against a metal member whose edge is to be shaped and forming a groove along and in one surface thereof. Subsequently, a portion is severed from said member by flame cutting lengthwise of the groove, the cut extending from the wall of the groove through the remaining thickness of the member to the surface of the member opposite that having the groove.